You weren't talking about law enforcement, you were talking about an EMS who probably just saw them lying on the floor.
As for them being identical, they are very slightly different, but someone seeing them lying on the floor at a distance probably wouldn't be able to distinguish them. For example, here is a .223 and a 5.56 casing, both of them reloaded with .223 bullets. Can you tell which is which from just glancing at this photo? Even if you can, could you imagine how hard it would be too make that call if there wasn't the other casing to compare against, and you were only looking at one type?:
